Method for measuring heat and pressure characteristics of fusing apparatus

ABSTRACT

A method for measuring heat and pressure characteristics of a fusing contact arc or nip formed between heat and pressure fusing rolls for fusing powder images onto a copy sheet. A toner powder pattern is formed on a first strip of paper. A second strip of paper is placed in overlying position with the first strip of paper to form the nip measurement device. The two strips are positioned between the opened nip of heat and pressure fusing rolls which are then closed for a predetermined time. Upon separation of the rolls the two strips of paper are removed and stripped apart. A portion of toner powder pattern is offset from the first strip of paper onto the second strip of paper indicating immediately heat and pressure charactersitics of the fusing nip.

United States Patent Hendriekson Jan. 21, 1975 [75] Inventor: James A. Hendriekson, Rochester,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

221 Filed: June 14.1973

[21] Appl. No.: 370,182

[52] US. Cl 73/432 R [51] Int. Cl ..G01n 17/00, GOld 21/00 [58] Field of Search 432/59-62, 432/227-231: 219/216. 388; 73/339, 432;

[56] References Cited UNITED STATES PATENTS 3,649,117 3/1972 Weigle 355/[2 Primary ExaminerSv Clement Swisher [57] ABSTRACT A method for measuring heat and pressure characteristics of a fusing contact are or nip formed between heat and pressure fusing rolls for fusing powder images onto a copy sheet. A toner powder pattern is formed on a first strip of paper. A second strip of paper is placed in overlying position with the first strip of paper to form the nip measurement device. The two strips are positioned between the opened nip of heat and pressure fusing rolls which are then closed for a predetermined time. Upon separation of the rolls the two strips of paper are removed and stripped apart. A portion of toner powder pattern is offset from the first strip of paper onto the second strip of paper indicating immediately heat and pressure eharactersitics of the fusing nip.

6 Claims, 6 Drawing Figures PATENTEI] JANZI I975 SHiEI 2 BF 2 FIG. 20 FIG. 2b FIG. 2c

FIG. 4

FIG. 3

METHOD FOR MEASURING HEAT AND PRESSURE CHARACTERISTICS OF FUSING APPARATUS This invention relates to a method for measuring heat and pressure characteristics of a fusing apparatus for use with an electrostatic reproduction system to facilitate obtaining high quality copies.

It has been recognized that one of the preferred ways for fusing a powder image to a substrate is to bring the powder into direct contact with a hot surface, such as a heated roller. The roller surface may be dry, i.e., no application of a liquid release agent to the surface of that roller as described, for example, in U.S. Pat. Nos. 3,498,596, 3,539,l6l, and 3,666,247. Alternatively, the fuser roll surface may be melted with a release agent such as silicone oil as described in U.S. Pat. Nos. 3,268,351, and 3,256,002.

It has been found that the measurement of the pressure and temperature in the contact are or nip of the rolls is desirable from the standpoint of adjusting the nip to obtain high quality fixing of copy sheets. Therefore, the ease with which these parameters can be immediately ascertained under varying conditions can be extremely advantageous in the set up of a machine in the minimum time.

The present invention is for a method and device for rapidly ascertaining the pressure and temperature level of the nip formed by heat and pressure fusing rolls used in reproduction machines. This is accomplished generally speaking by offsetting a portion of a toner pattern from a strip onto another strip for immediate analysis.

It is therefore the principal object of the present invention to improve heated pressure fusing roll devices.

It is a further object of the present invention to facilitate the measurement of pressure and heat levels in the nip of fusing rolls.

It is a further object of the present invention to improve significantly the quality of fixes produced by heated pressure fusing rolls.

It is a further object of the present invention to detect wear and/or damage in the construction of heated and pressure fusing rolls.

These as well as other objects of the invention and further features thereof will be better understood upon reference to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. I illustrates schematically a xerographic reproducing apparatus incorporating a heated pressure fuser roll apparatus having a nip of the type measured in accordance with the present invention;

FIGS. 2ac are side views of the fusing rolls illustrating the nip measurement steps in sequence;

FIG. 3 is an enlarged portion of the nip measuring strip bearing a toner pattern indicating heat and pressure characteristics of the nip according to the invention; and

FIG. 4 is a view similar to FIG. 3 illustrating the corresponding ofi'set toner pattern onto a second strip measuring heat and pressure characteristics of the nip.

Referring now to the drawings, there is shown in FIG. I an automatic xerographic reproducing machine incorporating heat and pressure fusing rolls having a nip measured according to the invention. The automatic xerographic reproducing machine includes a xerographic plate or surface formed in the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow. The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations. For the purpose of the present disclosure the several xerographic processing stations in the path of movement of the plate surface may be described functionally as follows:

A charging station A, at which a uniform electrostatic charge is deposited on the photoconductive plate;

An exposure station B, at which light or a radiation pattern of copies to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copy to be reproduced;

A developing station C, at which xerographic developing material, including toner particles having an electrostatic charge opposite that of the latent electrostatic image, is cascaded over the latent electrostatic image to form a toner powder image in configuration of the copy being reproduced;

A transfer station D at which the toner powder image is electrostatically transferred from the plate surface to a transfer material or a support surface mode of paper;

A drum cleaning and discharge station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and at which the plate is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon, and

A fusing station F at which the toner powder image is affixed to the paper support material by fusing rolls 103 and 105 which apply heat and pressure at a nip as will be described hereinafter.

The description of the xerographic process is consid ered sufficient for an understanding of the instant invention. Further details may be had by reference to U.S. Pat. No. 3,578,859 filed July 3, 1969 and commonly assigned herewith.

The quality of the copies produced by the machine is greatly affected by the heat and pressure fusing characteristics at the nip formed fuser roll I03 and pressure roll 105. The fusing rolls may be wetted or dry as described above. In either case the nip pressure and heat are critical in obtaining high quality fusing. For a typical dry system the fuser or heated roll I03 comprises a rotating member I30 having an elastic compressible coating 132 made of silicone rubber or any suitable heat resistant compressible material as described for example in the aforementioned patents. The rotating member I30 may be internally heated by a heat source 134 as described in U.S. Pat. No. 3,666,247 or externally heated as described in U.S. Pat. Nos. 3,498,596 and 3,539,161. The pressure on backup roll 105 comprises a rotating member I40 which is covered with an elastic layer I42. When the two rolls I03 and I05 are engaged the applied load deforms the rubber in the pressure roll to provide the nip with a finite width. The copy sheet electrostatically bearing the toner images on the underside is brought into contact with the nip of the rolls with the toner image contacting the fuser roll I03.

For a given temperature of the fuser roll, the fusing rate will depend upon the contact arc length of the support material against the dwell time, i.e., the time the toner images remain between the fuser roll I6 and the backup roll 18. Dwell time can be varied either by changing the surface velocity of the rolls or by varying the contact arc length and holding the speed of the roll the same. Contact arc length depends on the softness of the rubber on back-up roll 105 and on the amount of pressure between the rolls I03 and 105. The mechanism for driving the rolls and for lowering and raising the rolls into contact can be accomplished by any suitable means as that described, for example, in US. Pat. No. 3,291,466 or by a suitable mechanical camming device. The subject invention is concerned with the immediate determination of the heat and pressure characteristics of the contact arc or nip.

Referring specifically to FIGS. 2a-c there is shown in sequence the steps for measuring the heat and pressure characteristics of the contact are or nip formed by the fusing rollers. A measurement device 200 comprises a strip of paper 201 having a uniform toner pattern 215 which may be formed by the electrostatic copying machine and toner material used as described above. A half tone pattern is very good for this purpose as best shown in FIG. 3. Another strip of paper 210 which is unmarked is positioned in overlying relationship with strip Strips 201 and 210 are inserted between the fusing rollers 103 and 105 while the rollers are separated as in FIG. 2a. Next the fusing rollers are closed to form an operating nip for a predetermined time as in FIG. 2b. Preferably, this time period ranges from about the shortest dwell time or about 0.2 seconds to about 6 seconds depending upon melting point, viscosity, roll temperature and sheet material.

Any suitable pigmented or dyed electroscopic toner material may be employed with the carriers of this invention. Typical toner materials include: gum copal; gum sandarac; rosin; cumaromeindene resin; asphaltum; phenol formaldehyde resins; rosin modified phenol formaldehyde resins; epoxy resins; polyethylene resins; polyester resins and mixtures thereof. The particular toner material to be employed usually depends upon the separation of the toner particles from the car rier beads in the triboelectric series and whether a negatively or positively charged image is to be developed. Among the patents describing electroscopic toner compositions are US. Pat. No. 2,659,670 to Copley; U.S. Pat. No. 2,753,308 to Landrigan; U.S. Pat. No. 3,079,342 to lnsalaco; US. Pat. Re-issue 25,136 to Carlson, and U.S. Pat. 2,788,288 to Rheinfrank et al. These toners generally have an average particle diameter between about i and 30 microns. A toner comprising a styrene-N-butyl methacrylate eopolymer, polyvinylbutyral and carbon black produced by the method disclosed by M. A. lnsalaco in Example I of US. Pat. No. 3,079,342 is preferred because of its excellent tri boelectric qualities and its deep black color.

In the next step the fusing rollers are separated from each other to an inoperative position. The strips 201 and 210 are removed and separated whereupon a portion 220 of the toner pattern 215 in the vicinity of the nip is offset from strip 20] onto strip 210 as best shown in FIGS. 3 and 4.

It will be appreciated that the width of the offset toner portion 220 can be used to determine the fusing quality of the fusing rollers. Thus, if there is too much pressure there will be an increase over the standard nip width normally offset for the machine operating conditions. On the other hand, if there is insufficient pressure in the nip, the width will be decreased from the standard. Also the density of the nip width offset is useful to determine the temperature level of the nip. More specifically, if there is insufficient heat at the fusing nip there is poor transfer of offset portion 220 to strip 210. On the other hand if the temperature is elevated beyond a standard temperature range the sheet 210 will become discolored or scorched.

It will be further appreciated that by observing the strip 201 and strip 210 that the toner pattern 215 and offset portion 220 in FIGS. 3 and 4 serve to determine immediately the heat and pressure levels of the nip formed by the fusing rolls. It will be noted that if the transfer of offset portion 220 is uniform in density and a width meeting standard specifications, then the fix level of the fusing apparatus is acceptable. With this in mind the pressure and/or temperature of the nip can be adjusted and the tests easily repeated until the desired operating conditions are obtained. Also the image will not bleed or fade and is resistant to fluids and therefore is a permanent record. Moreover, since the toner material is the same as is used in the machine processor during operating conditions, the toner material serves as a measurement reference as well.

While there have been shown and described and pointed out the fundamental novel features of the in vention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the inven tion.

What is claimed is:

l. A method of measuring heat and pressure characteristics of a fusing nip between heat and pressure fusing rolls comprising the steps forming a toner pattern on a first strip of support ma terial,

positioning second strip of support material in overly ing relationship with said first strip,

inserting said first and second strips between heat and pressure fusing rolls while spaced apart, closing the fusing rolls to form a nip at operating con ditions for a predetermined time,

separating the rolls and removing said strips from the fusing rolls, and

separating said strips to effect offset of a portion of the toner pattern from said first strip onto said second strip to measure heat and pressure characteris tics of the nip.

2. A method according to claim I wherein only on of the rolls is heated.

3. A method according to claim 1 wherein each of the rolls is heated.

4. A method according to claim I wherein at least one of said strips of support material is made of paper.

5. A method according to claim 1 wherein both of said strips of support material are made of paper.

6. A method according to claim 2 wherein said toner pattern is formed by electrostatic process steps. 

1. A method of measuring heat and pressure characteristics of a fusing nip between heat and pressure fusing rolls comprising the steps forming a toner pattern on a first strip of support material, positioning second strip of support material in overlying relationship with said first strip, inserting said first and second strips between heat and pressure fusing rolls while spaced apart, closing the fusing rolls to form a nip at operating conditions for a predetermined time, separating the rolls and removing said strips from the fusing rolls, and separating said strips to effect offset of a portion of the toner pattern from said first strip onto said second strip to measure heat and pressure characteristics of the nip.
 2. A method according to claim 1 wherein only on of the rolls is heated.
 3. A method according to claim 1 wherein each of the rolls is heated.
 4. A method according to claim 1 wherein at least one of said strips of support material is made of paper.
 5. A method according to claim 1 wherein both of said strips of support material are made of paper.
 6. A method according to claim 2 wherein said toner pattern is formed by electrostatic process steps. 